The present invention relates to a method and apparatus for determining a zero position of a yarn guide of a winding device of a textile machine producing cheeses, and relates more particularly to such a textile machine which is capable of cross-winding cheeses by means of a step motor.
For producing a textile bobbin, it is known to be necessary, on the one hand, to put the respective textile bobbin into rotation and, on the other hand, to cross-wind the yarn running up on the bobbin along the bobbin axis. By means of a relatively rapid cross-winding of the yarn, it is possible to produce a so-called cross-wound textile bobbin, which is not only distinguished by a comparatively stable bobbin body, but also by good unwinding properties.
In connection with the production of such cheeses, there are already different yarn placement systems in actual use, which are extensively described in numerous patent applications.
For example, in connection with bobbin-winding machines operated at relatively high winding speeds, the use of so-called yarn guide drums as yarn cross-winding devices is widespread. Such yarn guide drums have a groove for cross-winding the yarn and at the same time they drive the textile bobbin by frictional contact. However, such yarn guide drums, which have proven themselves per se, are relatively expensive to produce and, because of the limits of the system, can only be used for producing cheeses of the “random cross-wound” type, since for producing a so-called “precision,” or “stepped precision winding,” the drive mechanism of the cheese and the drive mechanism of the-yarn cross-winding device must be separate.
Different yarn cross-winding devices are known in connection with winding heads which respectively have a separate drive mechanism for rotating the take-up bobbin and a separate drive mechanism for cross-winding the arriving yarn. For example, cross-winding devices are known which have a yarn guide which can be shifted parallel with the axis of rotation of the cheese and are for example connected via traction means with a reversible individual drive mechanism. Installations are furthermore known which operate with a so-called finger yarn guide, i.e. a yarn guide which has a finger-like yarn displacement lever, which is pivotable-through a specific angular range around an axis which is arranged substantially perpendicularly in relation to the cheese axis.
Yarn cross-winding devices with a yarn guide which can be shifted parallel in relation to the axis of rotation of the cheese have been described, for example, in German Patent Publication DE 37 34 478 A1, in German Patent Publication DE 100 21 963 A1 or in the later published German Patent Publication DE 10 2004 003 173.8.
The yarn cross-winding device described in German Patent Publication DE 37 34 478 A1 has a yarn guide which is guided on a yarn guide rod in the cross-winding area and is driven via endless traction means by a microprocessor-controlled step motor.
A yarn cross-winding device is also described in the later published German Patent Publication DE 10 2004 003 173.8, whose yarn guide is guided on a yarn guide rod and is connected via a toothed belt with a reversible individual drive mechanism. Here, the yarn guide rod, the gear wheels for the toothed belt, as well as the associated individual drive mechanisms are arranged in a housing which is closed to the greatest possible extent. This means that the interior of this yarn cross-winding device, embodied as a modular structural component, is sealed at the front by the endless traction means.
A yarn cross-winding device with a cross-winding yarn guide which is fixed on an endless belt and can be operated by an individual drive mechanism is furthermore described in German Patent Publication DE 100 21 963 A1. Here, the individual drive mechanism of the yarn guide can be controlled in such a way that a cross-winding stroke can be performed which can be changed in length. To this end, the individual drive mechanism of the cross-winding yarn guide is equipped with an angle encoder which detects the rotor position of the electric motor and reports the detected rotor position to a corresponding work station control.
However, in connection with the above-mentioned generally advantageous yarn cross-winding devices, the comparatively large control outlay, which is performed for assuring a correct traversing of a yarn, is disadvantageous. Thus, the known yarn cross-winding devices have relatively elaborate, and therefore expensive control and monitoring devices.